It is well known that flat panel displays such as liquid crystal displays and organic EL displays have a structure in which a thin film transistor (hereinafter, referred to as “TFT”) is formed on a glass substrate or the like. Meanwhile, in response to the recent requirement of an increase in the size and definition of thin televisions, there has been a demand for large and high-definition display panels using the above-described TFT (TFT panels).
In the related art, it was common to use a wiring film made of an aluminum (Al)-based material as the wiring film for gate electrodes, source electrodes, drain electrodes, and the like in the large and high-definition TFT panels; however, in recent years, in order to decrease the resistance of the wiring film, there have been attempts to use a copper (Cu)-based material having a higher conductivity than Al.
While there have been many proposals regarding a variety of copper alloys as the copper-based material intended to be used as the wiring film in the TFT panel, in recent years, as described in, for example, PTL 1 and 2, Cu—Ca alloys have been drawing attention. A wiring film made of a Cu—Ca alloy does not only have a lower resistivity than an Al-based material but also has excellent adhesiveness to glass or the like which is a substrate. In a case in which the wiring film in the TFT panel is formed of the above-described Cu—Ca alloy, it is common to apply sputtering and, in this case, a sputtering target made of the Cu—Ca alloy is used.